diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 1834e55..ec891e3 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -264,8 +264,13 @@ function comment_field_config_delete(FieldConfigInterface $field) {
  */
 function comment_field_config_insert(FieldConfigInterface $field) {
   if ($field->getType() == 'comment') {
+    // Check that the target entity type uses an integer ID.
+    $entity_type_id = $field->getTargetEntityTypeId();
+    if (!_comment_entity_uses_integer_id($entity_type_id)) {
+      throw new \UnexpectedValueException(t('You cannot attach a comment field to an entity with a non-integer ID field.'));
+    }
     // Delete all fields and displays attached to the comment bundle.
-    entity_invoke_bundle_hook('insert', 'comment', $field->getTargetEntityTypeId() . '__' . $field->getName());
+    entity_invoke_bundle_hook('insert', 'comment', $entity_type_id . '__' . $field->getName());
   }
 }
 
@@ -812,6 +817,11 @@ function comment_form_field_ui_field_overview_form_alter(&$form, $form_state) {
   if ($form['#entity_type'] == 'comment' && $request->attributes->has('commented_entity_type')) {
     $form['#title'] = \Drupal::service('comment.manager')->getFieldUIPageTitle($request->attributes->get('commented_entity_type'), $request->attributes->get('field_name'));
   }
+  $entity_type_id = $form['#entity_type'];
+  if (!_comment_entity_uses_integer_id($entity_type_id)) {
+    // You cannot use comment fields on entity types with non-integer IDs.
+    unset($form['fields']['_add_new_field']['type']['#options']['comment']);
+  }
 }
 
 /**
@@ -937,6 +947,24 @@ function comment_entity_predelete(EntityInterface $entity) {
 }
 
 /**
+ * Determines if an entity type is using an integer-based ID definition.
+ *
+ * @param string $entity_type_id
+ *   The ID the represents the entity type.
+ *
+ * @return bool
+ *   Returns TRUE if the entity type has an integer-based ID definition and
+ *   FALSE otherwise.
+ */
+function _comment_entity_uses_integer_id($entity_type_id) {
+  $entity_type = \Drupal::entityManager()->getDefinition($entity_type_id);
+  $entity_type_id_key = $entity_type->getKey('id');
+  $field_definitions = \Drupal::entityManager()->getBaseFieldDefinitions($entity_type->id());
+  $entity_type_id_definition = $field_definitions[$entity_type_id_key];
+  return $entity_type_id_definition->getType() === 'integer';
+}
+
+/**
  * Implements hook_node_update_index().
  */
 function comment_node_update_index(EntityInterface $node, $langcode) {
diff --git a/core/modules/comment/src/Tests/CommentNonNodeTest.php b/core/modules/comment/src/Tests/CommentNonNodeTest.php
index b5bb317..8f53832 100644
--- a/core/modules/comment/src/Tests/CommentNonNodeTest.php
+++ b/core/modules/comment/src/Tests/CommentNonNodeTest.php
@@ -382,4 +382,20 @@ function testCommentFunctionality() {
     $this->assertNoFieldByName('comment_body[0][value]', '', 'Comment field found.');
   }
 
+  /**
+   * Tests comment fields are not available for entity types with string ids.
+   */
+  public function testsStringIdEntities() {
+    // Create a bundle for entity_test.
+    entity_test_create_bundle('entity_test', 'Entity Test', 'entity_test_string_id');
+    $limited_user = $this->drupalCreateUser(array(
+      'administer entity_test_string_id fields',
+    ));
+    $this->drupalLogin($limited_user);
+    // Visit the Field UI overview.
+    $this->drupalGet('entity_test_string_id/structure/entity_test/fields');
+    // Ensure field isn't shown for string ids.
+    $this->assertNoOption('edit-fields-add-new-field-type', 'comment');
+  }
+
 }
diff --git a/core/modules/comment/src/Tests/CommentStringIdEntitiesTest.php b/core/modules/comment/src/Tests/CommentStringIdEntitiesTest.php
new file mode 100644
index 0000000..014b3b1
--- /dev/null
+++ b/core/modules/comment/src/Tests/CommentStringIdEntitiesTest.php
@@ -0,0 +1,57 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\comment\Tests\CommentStringIdEntitiesTest.
+ */
+
+namespace Drupal\comment\Tests;
+
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests that comment fields cannot be added to entities with non-integer IDs.
+ */
+class CommentStringIdEntitiesTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('comment', 'user', 'field', 'field_ui', 'entity_test');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Comments on Entity Types with string IDs',
+      'description' => 'Test that comment fields cannot be added to entities with non-integer IDs',
+      'group' => 'Comment',
+    );
+  }
+
+  public function setUp() {
+    parent::setUp();
+    $this->installEntitySchema('comment');
+    $this->installSchema('comment', array('comment_entity_statistics'));
+  }
+
+  /**
+   * Tests that comment fields cannot be added entities with non-integer IDs.
+   */
+  public function testCommentFieldNonStringId() {
+    try {
+      $field = entity_create('field_config', array(
+        'name' => 'foo',
+        'entity_type' => 'entity_test_string_id',
+        'settings' => array(),
+        'type' => 'comment',
+      ));
+      $field->save();
+      $this->fail('Did not throw an exception as expected.');
+    }
+    catch (\UnexpectedValueException $e) {
+      $this->pass('Exception thrown when trying to create comment field on Entity Type with string ID.');
+    }
+  }
+
+}
diff --git a/core/modules/system/tests/modules/entity_test/src/Entity/EntityTestStringId.php b/core/modules/system/tests/modules/entity_test/src/Entity/EntityTestStringId.php
new file mode 100644
index 0000000..627d3a5
--- /dev/null
+++ b/core/modules/system/tests/modules/entity_test/src/Entity/EntityTestStringId.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\entity_test\Entity\EntityTestStringId.
+ */
+
+namespace Drupal\entity_test\Entity;
+use Drupal\Core\Field\FieldDefinition;
+use Drupal\Core\Entity\EntityTypeInterface;
+
+/**
+ * Defines a test entity class with a string ID.
+ *
+ * @ContentEntityType(
+ *   id = "entity_test_string_id",
+ *   label = @Translation("Test entity with string_id"),
+ *   controllers = {
+ *     "access" = "Drupal\entity_test\EntityTestAccessController",
+ *     "form" = {
+ *       "default" = "Drupal\entity_test\EntityTestForm"
+ *     },
+ *     "translation" = "Drupal\content_translation\ContentTranslationHandler"
+ *   },
+ *   base_table = "entity_test_string",
+ *   fieldable = TRUE,
+ *   field_cache = TRUE,
+ *   entity_keys = {
+ *     "id" = "id",
+ *     "uuid" = "uuid",
+ *     "bundle" = "type"
+ *   },
+ *   links = {
+ *     "canonical" = "entity_test.render",
+ *     "edit-form" = "entity_test.edit_entity_test_string_id",
+ *     "admin-form" = "entity_test.admin_entity_test_string_id"
+ *   }
+ * )
+ */
+class EntityTestStringId extends EntityTest {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
+    $fields = parent::baseFieldDefinitions($entity_type);
+    $fields['id'] = FieldDefinition::create('string')
+      ->setLabel(t('ID'))
+      ->setDescription(t('The ID of the test entity.'))
+      ->setReadOnly(TRUE);
+    return $fields;
+  }
+
+}
diff --git a/core/modules/system/tests/modules/entity_test/src/Routing/EntityTestRoutes.php b/core/modules/system/tests/modules/entity_test/src/Routing/EntityTestRoutes.php
index 7f608e6..ccbc414 100644
--- a/core/modules/system/tests/modules/entity_test/src/Routing/EntityTestRoutes.php
+++ b/core/modules/system/tests/modules/entity_test/src/Routing/EntityTestRoutes.php
@@ -22,6 +22,7 @@ class EntityTestRoutes {
    */
   public function routes() {
     $types = entity_test_entity_types();
+    $types[] = 'entity_test_string_id';
 
     $routes = array();
     foreach ($types as $entity_type) {